Selecting heat sinks for heavily populated boards

摘要

When facing the task of cooling heavily populated PCBs (printed-circuit boards), designers must understand that careful management of airflow along the boards is the key to effective cooling. In these dense-PCB applications, pressure drop isrnas important as thermal resistance when it comes to selecting heat sinks. Designers regularly use the parameters of thermal resistance and pressure drop to quantify the performance of heat sinks. Thermal resistance, the temperature increase in degrees Celsius per watt, measures how effectively a heat sink transfers heat from the heat-generating device to the ambient environment. The lower the thermal resistance, the more effective the heat sink because heat sinks with low thermal resistance can cool heavier heat loads before the heat-generating device reaches its maximum allowed temperature. Thermal-resistance values for heat sinks are a function of the airflow through the heat sink. In other words, faster airflow results in lower thermal-resistance values.